The long-awaited criminal trial of the business tycoon Asil Nadir has been hampered once more after investigators examining the 17-year-old evidence fell ill because of a bacterial infection found in the files.

Mr Nadir, who is now 69, fled from Britain in 1993 just before he was due to stand trial on charges of theft relating to a £34m fraud connected to the collapse of his Polly Peck business empire.

At the time, Mr Nadir claimed he would not receive a fair trial. However, he returned to the UK from the Turkish Republic of Northern Cyprus last month and is expected to face trial next year.

But yesterday at the second hearing at the Old Bailey since his return, the court was told of two factors which could potentially complicate the trial further. The first was not entirely unexpected: that 18 potential witnesses in the case have died. But the second factor was quite bizarre.

Philip Shears QC, prosecuting, explained that fraud investigators had been struck down by a bug from some of the 1,400 boxes of papers being resurrected from storage for the case. This had resulted in one member of staff being treated in hospital and other staff being ordered to wear protective clothing.

"A microbial organism caused one member to go to hospital for burns and difficulties," Mr Shears said. "Health and safety issues have had to be thought about."

In addition to issuing staff with masks, goggles and aprons, some 900 boxes would be given thermal treatment "to negate it", the barrister added. The trial judge, Mr Justice Holroyde, sympathised with staff but added: "Let's hope there will be no damage to the documents."

Mr Shears added that the 18 witnesses were among 283 people being traced by the Serious Fraud Office (SFO) following Mr Nadir's return to the UK. The barrister said that 201 witnesses had been traced.

It was previously explained that, because of the passage of time and questions about the reliability of evidence which would ideally have been heard 17 years ago, Mr Nadir is expected to face a much smaller charge sheet than the 66 counts he faced in 1993.

Mr Nadir is due to face trial in October next year, and was appearing yesterday at a directions hearing. Wearing a dark grey suit with a white silk handkerchief in his breast pocket, he was – in an unusual move – allowed to leave the dock and sit next to his solicitor in the well of the court. The judge said he was acceding to a request from the defence only because he had been informed that Mr Nadir had a hearing difficulty.

During yesterday's hearing, the defence's counsel, William Clegg QC, complained to Mr Justice Holroyde that Richard Alderman, the director of the SFO, had made "a mischievous attempt to manipulate the press". Mr Clegg said Mr Alderman had tried to gain favour for the SFO in an article in a national newspaper. The court was told that Mr Alderman had no further plans to comment on the case.

Mr Justice Holroyde said: "There is, of course, a public interest in this case. It is entirely appropriate that the press should publish legitimate reports of the proceedings." But he gave warning that nothing should be published which prejudiced one side or another.

Remanding Mr Nadir on bail – which includes an electronic-tagging condition – the judge reminded him that if he did not turn up, the court could continue the case without him.

Mr Nadir replied: "I understand, my lord, and I have been attending meticulously."